Many modern products that we take for granted include integrated circuits. These tiny devices are used in common products and systems such as wireless communication, industrial robotics, spacecraft, and a vast array of consumer products such as cell phones, portable computers, music players, and automobiles. Across virtually all applications, there continues to be demand for increasing functions and reducing the size of the devices.
Manufacturing such devices typically utilizes various techniques, such as layering, doping, masking, and etching, to build electrical components on a substrate. The components are then interconnected to define specific electric circuits, such as a processors or memory including storage. Integrated circuits development is driven by reduced size, lower power consumption, and increased operating speed.
The integrated circuit contains semiconductor devices, such as transistors, capacitors and resistors, formed on the silicon substrate. The electrical connections used to connect the integrated circuits to form a working device are known as “interconnects”. Interconnects consist of conductive lines formed in the plane of the substrate, and contacts formed in the direction perpendicular to the plane of the substrate. Several interconnect levels may be used in the integrated circuit sometimes eight or more levels.
High quality contacts are essential to high device yield and reliability, but fabrication of these high quality contacts poses several technical challenges. For example, the contacts are designed to have a high ratio of the height to the diameter, known as the aspect ratio. High aspect ratio is a consequence of several constraints in the design of the IC.
For example, it is desirable to achieve a high packing density of the contacts to enable high circuit density. This constrains the diameter of the contacts to be as small as possible. In addition, the dielectric separating the semiconductor devices from the first metal level must be thick enough to protect transistors. The contacts often span the thickness of dielectric over a transistor and transistor gate over the substrate. These constraints lead to contacts with aspect ratios large enough to present manufacturing challenges.
As integrated circuit technology become smaller, the large aspect ratio combined with very small geometries creates many manufacturing and performance issues. Current attempts to manufacture very small contacts have been plagued with very high resistance. These contact resistances can dominate integrated circuit performance particularly with small process geometries such as thirty-two nanometers.
Several attempts have been made to improve some of the several components of contact resistance. For example, changing silicide interfaces or metallization materials have fallen short of the demands for smaller technology nodes. Containing metallization materials and resistance in materials at dimensions that fall below material characteristics such as mean free path of electrons are prohibitive.
Thus, a need still remains for an integrated circuit system to improve contact performance and reliability particularly with small geometry technology nodes. In view of the ever-increasing commercial competitive pressures, coupled with the technical imperatives of improved die-to-die variation and improved production efficiency, it is critical that answers be found for these problems. Competitive pressures also demand lower costs alongside improved efficiencies and performance.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.